In a conventional second generation mobile communications system, for example operated under the Global System for Mobile Communications (GSM), a mobile subscriber is typically charged an amount which depends on the duration of his connection to the network. In the case of a prepaid phone, a subscriber pays in advance, and receives a corresponding credit.
EP-A-1030506 shows a prepaid mobile phone, which has a display, which displays the current credit value numerically on the display of the phone.
By contrast, in a third generation mobile communications system, for example operated under the General Packet Radio Service (GPRS) digital cellular telecommunications system, it is envisaged that subscribers will advantageously be able to maintain a permanent network connection. In this case, it may be inappropriate to charge the subscriber an amount which is dependent on the duration of the connection to the network. Rather, it may be more appropriate to make a charge which is related to the amount of data exchanged between the subscriber and the network.
One possibility is that a network operator may make a basic charge, for example monthly, with the subscriber being allowed to send or receive a specified amount of data within that basic charge.